Non-metallic orthopedic plate

ABSTRACT

A spinal plate comprises a body portion and at least one locking mechanism for engaging the body portion. The body portion is made of a radiolucent material, such as a polymer or polyether ether ketone (PEEK), and includes a plurality of bone screw openings for receiving a plurality of bone screws, such as bone screws. The at least one locking mechanism is for securing at least one of the plurality of bone screws when received into the body portion.

FIELD OF THE INVENTION

The present invention relates generally to bone plating systems, andmore particularly, to a plating system for use in the treatment ofvarious orthopedic pathologies.

BACKGROUND

The treatment of injuries to the spine has advanced significantly,including treatment for many forms of spinal injury and deformities thatcan occur due to disease, congenital effects, the effects of tumors,and, of course, fractures and dislocations attributable to physicaltrauma. For many years, the use of elongated rigid plates has beenhelpful in the stabilization and fixation of the spine.

It has been found that many plate designs allow for a uni-cortically orbi-cortically intrinsically stable implant. It has also been found thatfixation plates can be useful in stabilizing the upper or lower cervicalspine in traumatic, degenerative, tumorous or infectious processes.Moreover, these plates provide the additional benefit of allowingsimultaneous neural decompression with immediate stability.

During the many years of development of cervical plating systems,particularly for the anterior approach, various needs for such a systemhave been recognized. For instance, the plate must provide strongmechanical fixation that can control movement of each vertebral motionsegment in six degrees of freedom. The plate must also be able towithstand axial loading in continuity with each of the three columns ofthe spine. The plating system must be able to maintain stress levelsbelow the endurance limits of the material, while at the same timeexceeding the strength of the anatomic structures or vertebrae to whichthe plating system is engaged.

Another recognized requirement for a plating system is that thethickness of the plate must be small to lower its prominence,particularly in the smaller spaces of the cervical spine. The screwsused to connect the plate to the vertebrae must not loosen over time orback out from the plate. Preferably the plate should be designed tocontact the vertebrae for greater stability.

On the other hand, while the plate must satisfy certain mechanicalrequirements, it must also satisfy certain anatomic and surgicalconsiderations. For example, the cervical plating system must minimizethe intrusion into the patient and reduce the trauma to the surroundingsoft tissue. It has also been found that optimum plating systems permitthe placement of more than one screw in each of the instrumentedvertebrae.

Many spinal plating systems have been developed in the last couple ofdecades that address some of the needs and requirements for cervicalfixation systems. One example is the Anterior Cervical Plating Systemdisclosed in U.S. Pat. No. 6,152,927, which is hereby incorporated byreference. However, even with the more refined plating system designs,there still remains a need for a spinal plating system that provides ahigh quality, durable device with modulus and mechanical strengthproperties similar to that of cortical bone. Metallic implants, with asubstantially higher modulus than cortical bone, can cause a phenomenonknown as “stress shielding,” which is commonly thought to lead to bonemass loss and the loosening and subsequent failure of some metallicorthopedic implants. Additionally, radiographic qualities of metallicimplants often produce imaging artifacts and scatter, which hinder theinspection of bone growth when using conventional imaging via X-ray, CATscanning, or MRI techniques.

SUMMARY

In order to address the needs left unfulfilled by prior systems, thepresent invention provides a novel orthopedic plate. In one embodiment,a bone plate comprises a body portion and at least one locking mechanismfor engaging the body portion. The body portion is made of a radiolucentmaterial, such as a polymer or polyether ether ketone (PEEK), andincludes a plurality of attachment mechanism openings for receiving aplurality of attachment mechanisms, such as bone screws. The at leastone locking mechanism is for securing at least one of the plurality ofattachment mechanisms when received into the body portion.

In some embodiments, the bone plate also includes at least one insertaffixable with the body portion, the insert for engaging with thelocking mechanism. The insert may comprise titanium, aluminum, or someother material that is different than the radiolucent material.

In some embodiments, the insert includes a rotation-prevention portionto thereby prevent rotation of the insert in the body portion. Theinsert may also include a metallic material for threadingly engagingwith the locking mechanism. Also, the insert may be positioned along alongitudinal axis of the body portion to simultaneously engage with aplurality of locking mechanisms.

In another embodiment, a bone plate comprises a body formed primarily ofa first material, wherein the body includes an opening for receiving anattachment mechanism, such as a bone screw. The bone plate alsocomprises an insert having one or more engaging portions, the insertincluding a second material different from the first material. The boneplate may also include a locking mechanism for engaging with theengaging portion. When engaged with the engaging portion, the lockingmechanism secures the attachment mechanism in the corresponding opening.

In some embodiments, the first material is radiolucent, and the secondmaterial is radio-opaque. Also in some embodiments, the second materialis harder than the first material.

In another embodiment, a spinal plating system is provided for promotingfusion between two or more vertebral bodies. The spinal plating systemincludes a plurality of attachment mechanisms, each of the attachmentmechanisms having a centerline, and a body formed primarily of anon-metallic radiolucent material. The body includes an upper and alower surface, and a plurality of attachment mechanism openings forreceiving the plurality of attachment mechanisms. The spinal platingsystem also includes at least one threaded insert formed primarily of ametallic material, the insert being insertable into the at least onelocking mechanism opening, wherein the threaded insert threadablyreceives the threaded locking mechanism, the threaded locking mechanismhaving a head that extends above the upper surface of the body. Eachlocking mechanism opening can be situated such that an attachmentmechanism received in one of the attachment mechanism openings islockably held by the threaded locking mechanism.

Many objects and benefits of the invention will become apparent uponconsideration of the following written description of the invention,together with the accompanying Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top perspective view of an anterior plating system accordingto one embodiment of the present invention.

FIG. 2 is a side elevational view of the plating system shown in FIG. 1.

FIGS. 3 a–3 g are top elevational views of a fixation plate inaccordance with different embodiments of the present invention, providedin different sizes and configuration.

FIG. 4 is a partial cross-sectional view of a plate according to anembodiment of the present invention with the fixed angle attachmentmechanisms disposed within bone holes in a plate and engaged within avertebra.

FIG. 5 is an enlarged end cross-sectional view of the plate according toan embodiment of the present invention with variable angle screwsdisposed in the plate and engaged in a vertebra.

FIG. 6 a is a bottom perspective view of an anterior plating systemaccording to another embodiment of the present invention.

FIG. 6 b is a top perspective view of a threaded insert for use with theanterior cervical plating system of FIG. 6 a.

FIG. 6 c is a side cross-sectional view of the plate shown in FIG. 6 ataken along line 6 c—6 c as viewed in the direction of the arrows.

FIG. 7 a is a bottom perspective view of an anterior plating systemaccording to another embodiment of the present invention.

FIGS. 7 b and 7 c are side cross-sectional views of the plate shown inFIG. 7 a taken along line 7 b—7 b and 7 c—7 c, respectively, as viewedin the direction of the arrows.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments, or examples,illustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is thereby intended. Any alterations andfurther modifications in the described embodiments, and any furtherapplications of the principles of the invention as described herein arecontemplated as would normally occur to one skilled in the art to whichthe invention relates.

One embodiment of a bone plating system or fixation assembly 30 isdepicted in FIGS. 1 and 2. In the present example, the bone platingsystem 30 is an anterior cervical plate, but it is understood that otherplating systems can also benefit from the present invention. Otherexamples include plates or bone repair systems that can be used in theleg, the arm, the foot, the hand, or other parts of the body.

In accordance with the present embodiment, the plating system includesan elongated plate 31 and one or more bone attachment mechanisms 32,such as bone screws. Other bone attachment mechanisms include bolts,staples, and protrusions that can help to secure the plate in a desiredposition. The attachment mechanisms may be held or retained to the plate31 by way of one or more locking assemblies 33. In the embodiments thatuse attachment mechanisms such as screws or bolts, the elongated plate31 is provided with a plurality of openings or holes 34 in a variety ofarrangements. The plate also can be divided into vertebral level nodes35 with the attachment mechanisms 32 and openings 34 aligned at eachnode. Further, the plate 31 includes recesses between each of the nodes35 to reduce the outer contour and size of the plate. In addition, thereduced width portion between each of the nodes 35 provides an area ofreduced material for additional bending of the plate as may be requiredby the spinal anatomy.

The plate 31 is constructed, primarily, of a radiolucent material, suchas a polymer based resin. In one embodiment, the plate 31 is constructedsubstantially from a polyether ether ketone (PEEK) high temperaturethermoplastic commercially available by Invibio Biomaterial Solutions ofLancashire, UK under the tradename PEEK-OPTIMA. Using such material,conventional imaging of bony structures associated with the plate 31,such as with X-ray, computerized axial tomography (CAT) scanning, ormagnetic resonance imaging (MRI) is improved due to the lack of imagingartifacts and scatter compared to that generated from metallic implants.Also, polymers such as PEEK will bow and bend to a limited degree. Thisflexibility can be used to provide better healing/fusion between thefractured bone or fused vertebral bodies by allowing increased relativemotion and avoiding stress shielding.

The plate 31 can further include one or more bone growth orfusion-promoting elements, such as bone, bone morphogenetic protein(BMP), demineralized bone matrix (DBM), LIM mineralization proteins(LMP), osteogenic pastes, and so forth. It is understood that suchfusion-promoting elements are well known by those of ordinary skill inthe art.

The plate 31 can include a rounded upper edge 36 to reduce irritation ofsurrounding tissue, for example, in a spinal fusion procedure, therounded upper edge would be in contact with the soft tissue surroundingthe spine. The rounded upper edge 36 reduces the amount of trauma orirritation that would be experienced by the surrounding soft tissue. Thebottom surface 37 of the plate 31 is preferably configured to contactand engage the fractured bone or vertebral bodies at each of theinstrumented levels of the spine. In some embodiments, the bottomsurface can be textured to enhance its grip on the vertebral body andmay have a longitudinal and/or transverse curvature to match thecorresponding attachment surface (e.g., the curve of the spine).

Referring now to FIGS. 3 a–3 g, several variations of the elongatedplate 31 are depicted. It is understood that the bone plating systemaccording to the present embodiment can be readily adapted to fixseveral fractured bony pieces or vertebrae, of course depending upon thesize/length of the plate and the number and arrangement of attachmentmechanisms. For example, the plate depicted in FIGS. 1, 2 and 3 aincludes five vertebral level nodes 35 a so that the plate can beengaged to five vertebrae of the spine. The plate 31 a of FIG. 3 a couldbe used to fix the vertebrae C2–C6, although the plate also may be usedin thoracic, lumbar, and sacral regions of the spine. The elongatedplates 31 b depicted in FIG. 3 b is sized and configured to span threevertebrae, depending upon the instrumented vertebral levels. In thisinstance, the plate 31 b includes three vertebral level nodes 35 b, withtwo nodes at the opposite ends of the plate and one node with attachmentmechanisms offset from each other in the middle portion of the plate toaccommodate variation in vertebral anatomy.

A modification of the plate 31 b is depicted in FIG. 3 c. In this case,the plate 31 c includes three nodes 35 c, with the nodes on the oppositeside of the middle portion of the plate being directly aligned at thesame vertebral level. The plates of FIGS. 3 d–3 e, namely plates 31 dand 31 e, are similar to the plate 31 c although their lengths areprogressively shorter to accommodate varying vertebral body height. Thelast two plates 31 f and 31 g, in FIGS. 3 f–3 g, respectively, providefor instrumentation of two vertebral levels, each having two nodes 35 fand 35 g, respectively.

The elongated plates 31 a–31 g can provide a variety of hole patterns ateach of the nodes 35 a–35 g. These hole patterns can provide for atleast two attachment mechanisms (e.g., screws) to be engaged into eachrespective bony portion (e.g., vertebral body). As discussed above, ithas been found that the placement of two or more screws in eachvertebral body improves the stability of the construct.

The present embodiments may also provide a mechanism for locking theattachment mechanisms to the elongated plate to prevent backout,loosening, or other dis-engagement of the attachment mechanisms.Consequently, in a further aspect of the embodiments, various openingshole patterns may be provided. One pattern is an end hole pattern 38, asshown at the ends of plate 31 in FIG. 1 and plate 31 a in FIG. 3 a. Inthis arrangement, two screw holes 34 are laterally disposed at a singlenode 35 a. A single locking assembly may be disposed between the twoscrew holes 34 and configured to lock attachment mechanisms disposedwithin the plate 31 a. The locking assembly can be a machine screw thatengages with threads in the plate 31 a, or can be a self-tapping screwthat cuts through the plate as it is advanced therein. Other types oflocking assemblies include a rotatable disk, lever, or rivet shaped toselectively allow one or more attachment mechanisms to be inserted andlocked; a deformable portion (e.g., a washer) that selectively allow oneor more attachment mechanisms to be inserted and locked; strap/tiemechanisms that can be used to selectively tie down one or moreattachment mechanisms; and a sliding member for moving between differentpositions to selectively allow one or more attachment mechanisms to beinserted and locked. A similar arrangement can be provided by the middlehole pattern 39 in which two screw holes are situated at a singlevertebral level. A locking assembly can be disposed between the twoattachment mechanism holes and configured to lock the respectiveattachment mechanisms.

The present embodiment further contemplates a plate carryingfour-attachment mechanism patterns. For the sake of example, thefour-hole pattern 40 illustrated in FIG. 1 and FIGS. 3 a and 3 d,provides for four bone screws holes in a diamond pattern. A singlelocking assembly 33 can be centrally disposed between all of theattachment mechanism holes so that attachment mechanisms within therespective holes are simultaneously locked by the single lockingassembly. In the five node plate 31 a of FIG. 3 a, two such four-holepatterns 40 are provided. In the three-node plate 31 d of FIG. 3 d, onlya single four-hole pattern 40 is required. It can be appreciated thatthe four-hole pattern 40 provides a great degree of flexibility to thesurgeon in determining how many attachment mechanisms 32 will be engagedinto a single vertebra, and in what arrangement. For example, as shownin FIG. 1, two screws are situated in the laterally opposite screw holesat the vertebral level node 35. Alternatively, attachment mechanismscould be placed in the longitudinally opposite screw holes orientedalong the length of the plate 31 a. Other arrangements contemplateattachment mechanisms being placed in immediately adjacent screw holes34, or placing three attachment mechanisms in three of the holes of thefour-hole pattern 40. Again, the selection of attachment mechanisms andtheir arrangement can be left to the surgeon and will be based upon thetype of correction or fixation required and the anatomy of bony memberbeing addressed.

A further arrangement for attachment mechanisms is provided by thefour-hole cluster 41 depicted in FIGS. 3 b and 3 c. In the four-holecluster 41 in plate 31 b, two hole pairs 41 a and 41 b are provided.Each of the hole pairs may include its own locking assembly to lock thetwo attachment mechanisms (e.g., screws) into the screw bores of therespective hole pairs. As shown in FIG. 3 b, the orientation of theparticular hole pairs provides one screw hole from each pair generallylaterally relative to each other in a single bony portion (e.g.,vertebra). The other of the attachment mechanism holes in eachrespective pair is longitudinally offset from the central screw holes,being disposed closer to the ends of the plate 31 b. In this manner, thetwo central holes of each of the two holes pairs can be engaged in asingle vertebra, while the remaining screw holes of the hole pairs 41 aand 41 b can be disposed in the superior and inferior adjacentvertebrae. Most preferably, however, each of the screw holes in thefour-hole cluster 41 is generally oriented over or slightly offset froma single vertebra. The surgeon then has the option to selected any ofthe screw holes in the two hole pairs 41 a or 41 b that is optimallyaligned over the vertebra.

A similar arrangement is found in the plate 31C which includes afour-hole cluster 42. In this example, it can be seen that the four-holecluster 42 includes two hole pairs 42 a and 42 b, in a manner similar tothe four-hole cluster 41 of FIG. 3 b; however in this case, the holepairs are arranged closer to each other, principally because the plate31 c is shorter than the plate 31 b. In both of the four-hole clusters40 and 41, the locking assemblies are provided to lock only a pair ofattachment mechanism holes rather than all four holes with a singlelocking assembly.

The invention further contemplates a three-hole pattern, such as pattern43 provided in the plate 31 f in FIG. 3 f. In this example, a singlelocking assembly is used to fix three attachment mechanisms within therespective screw holes. A five-hole pattern 44 is provided on plate 31g, as shown in FIG. 3 g. In this example, a single hole is arrangedcentrally between four outlying holes. Two locking assemblies 33 areprovided to lock a pair of the outlying four screw holes together withthe central hole. In this configuration, the central hole is held inplace by two locking assemblies, while each of the outlying pair ofholes is held in place by a single locking assembly.

Referring now to FIGS. 4 and 5, the use of the fixation plate assembly30 is illustrated using, for the sake of example, bone screws foraffixing to a vertebral body V. In FIG. 4, a pair of fixed angle screws50 are disposed within respective bores 34 so that the threaded shanks51 project beyond the lower surface 37 of the plate 31 and into thevertebral body V. The threaded shank is preferably configured to engagethe cortical and cancellous bone of the vertebral body V. Theintermediate portion 52 of the fixed angle screw 50 extends through thecylindrical bore 77 of the screw holes 34. The spherical surface 57 ofthe head 54 of the screw contacts the spherical recess 75 of the screwhole 34 as the fixed angle screw 50 is threaded into the vertebral bodyV. Once the screw 50 is completely seated within the spherical recess75, the intermediate portion 52 provides a snug relationship relative tothe cylindrical bore 77 so that the fixed angle screw 50 is not able topivot or translate relative to the plate 31.

In order to ensure secure fixation of the screw 50 within plate 31, thelocking assembly 33 is tightened onto the heads 54 of the two attachmentmechanisms 50. In particular, a locking mechanism 85, such as a lockingscrew, is threaded into the bore 70 to draw the washer 90 into contactwith the screw heads. In the present embodiment, the bore 70 is alreadytapped, although in other embodiments the locking mechanism 85 may be aself tapping screw. Further embodiments of the locking mechanism 85include a disk, lever, rivet, or other mechanical structure configuredor shaped to selectively allow one or more attachment mechanisms to beinserted and/or locked; a deformable portion (e.g., a washer) thatselectively allow one or more attachment mechanisms to be insertedand/or locked; strap/tie mechanisms that can be used to selectively tiedown one or more attachment mechanisms; and a sliding member for movingbetween different positions to selectively allow one or more attachmentmechanisms to be inserted and/or locked.

The convex surface 92 seats against the spherical surface 57 of theattachment mechanism heads 54 to firmly seat the screw heads within theplate spherical recess 75. In some embodiments, the locking washer 90can advance sufficiently far into the locking recess 71 to restsubstantially flush with the top surfaces 56 of the attachmentmechanisms 50.

In a further aspect of the present embodiments, the locking assembly 33can be loosely fixed on the plate 31 so that the surgeon does not haveto attach the locking assembly when the plate is engaged to a vertebraor other bony member. In the present example, the locking mechanism 85is a screw that is pre-threaded through the locking washer 90 and intothe tapped bore 70 until about three or fewer threads of the lockingscrew project below the bottom surface 37 of the plate. The lockingscrew 85 is then staked at the thread furthest from the plate so thatthe screw cannot be removed or backed out through the tapped bore 70. Ofcourse, the locking screw 85 can be advanced further through the bore70—when it is necessary to enable the locking assembly 33. As previouslymentioned, the sharp point 86 a of the locking screw 85 is preferablyconfigured to penetrate the cortical bone. With the locking screw stakedto the plate, the sharp point 86 a will penetrate the vertebra V whenthe plate 31 is initially positioned on the bone. In this instance, thelocking screw 85 helps locate and temporarily stabilize the plate on thevertebra V as the attachment mechanisms 50 are implanted into the bone.This temporary location feature provided by the locking screw 85 canalso be used when a drill guide is used to drill and tap the vertebra toreceive the attachment mechanisms 50.

The locking assembly 33 can be configured so that the washer 90 can bemoved clear of the screw holes 34 when the locking screw 85 is staked tothe plate 31. Thus, even with the locking assembly 33 in its loosenedposition, the attachment mechanisms 50, 60 can still be inserted intothe screw holes 34.

The use of the variable angle attachment mechanism 60 is depicted inFIG. 5. The locking assembly 33 functions as described above to lock theheads 64 of the variable angle screws 60 within the plate 31.Specifically, the convex surface 92 of the washer 90 contacts andapplies pressure to the spherical surfaces 67 of the respectiveattachment mechanisms 60. However, with the variable angle screws 60,the intermediate portion 62 does not fit snugly within the cylindricalbore 77 of the screw holes 34. Thus, even with the head 64 of each screw60 residing solidly within the spherical recess 75, the attachmentmechanism 60 can still be angulated relative to the plate and to theaxis of the spherical recess 75 and cylindrical bore 77. It isunderstood that the degree of angulation is restricted by the differencein diameters between the cylindrical bore 77 and the intermediateportion 62 of the variable angle screw 60. In one preferred embodiment,the relative diameters permit angulation of up to 20° from the axis 75 aof the recess 75 and bore 77.

During implantation, the variable angle capability of the screw 60allows the surgeon to place the attachment mechanism within the vertebraat any angle within the defined angulation limits (20° in one specificembodiment). Thus, the variable angle screw 60 provides greaterflexibility than does the fixed angle screw 50 for orienting theattachment mechanism relative to the anatomy of the vertebra. Moreover,this variable angle capability allows a limited degree of micro-motionbetween the screw and the plate when the fixation assembly 30 isimplanted within a patient. In other words, as the spine is loaded andas load is transmitted through the screws and plate, the plate andvertebra may translate relative to each other. The variable angle screw60 accommodates this relative movement by pivoting within the sphericalrecess 75. On the other hand, the fixed angle screw 50 prevents thisrelative movement. The choice between using a fixed or a variable anglescrew can be left to the surgeon depending upon the pathology beingtreated. The fixation plate assembly 30 according to the presentembodiment allows this choice to be made at any point during thesurgical procedure.

The plating system 30 of FIGS. 1–5 include many benefits. By using anon-metallic substance such as PEEK, the plate 31 obtains a degree offlexibility, when compared to metallic plates, while still providing astrong mechanical fixation that can control movement of each vertebralmotion segment in six degrees of freedom. The plating system 30 is alsobe able to withstand axial loading in continuity with each of the threecolumns of the spine. The plating system 30 is able to maintain stresslevels below the endurance limits of the PEEK material, while at thesame time exceeding the strength of the anatomic structures or vertebraeto which the plating system is engaged. The thickness of the plate 31 isrelatively small, thereby lowering its prominence, particularly in thesmaller spaces of the cervical spine. The PEEK material allows lockingscrews to be self-tapped, as contrasted with metallic plates. And, theflexible properties of the PEEK material help to prevent attachmentmechanisms from loosening or backing out from the plate 31 and thevertebral bodies.

Referring now to FIGS. 6 a–6 c, in another embodiment of the platingsystem 30, plate 31 h is similar to plate 31 f (FIG. 3 f) with theinclusion of a metallic insert 100. In the present embodiment, themetallic insert is made of titanium aluminum, or ceramic, although othermaterials can also be used. The metallic insert 100 is used for part ofthe locking assembly 33 to provide an improved interface for receivingand securing the locking screw 85.

Referring specifically to FIG. 6 b, the metallic insert 100 includes anoval shaped portion 102 and a cylindrical portion 104. The cylindricalportion 104 includes a threaded interior wall 106 for receiving andthreadingly engaging with the locking mechanism 85. Referring to FIGS. 6a and 6 c, in one embodiment, the metallic insert 100 is pressed intothe plate 31 h, preferably when the plate is in a more malleable state.

The plating system 30 of FIGS. 6 a–6 c include many benefits. Inaddition to the benefits listed above with reference to FIGS. 1–5, themetallic inserts 100 provide extra strength for the locking assemblies33. Also, the metallic inserts 100 are easily threaded, so that thelocking mechanism 85 can be of a very tight manufacture (e.g., a tightlythreaded screw as compared to a self-tapping screw). The oval shapedportion 102 prevents any rotation of the insert 100 when the lockingmechanism 85 is being inserted into or removed from the plating system30. Also, the oval shaped portion 102 prevents the insert from beingremoved in a direction opposite to the bottom surface 37 of the plate31.

Referring now to FIGS. 7 a–7 c, in another embodiment of the platingsystem 30, plate 31 i is similar to plate 31 e (FIG. 3 e) with theinclusion of a metallic insert 110. In the present embodiment, themetallic insert is made of titanium or aluminum, although othermaterials can also be used. The metallic insert 110 extends along alongitudinal axis of the plate 31 i, thereby stiffening andstrengthening the plate and reducing an amount of bow that wouldotherwise occur. The metallic insert 110 also provides anti-compressionstrength along its longitudinal axis. In some embodiments, the metallicinsert 110 provides one or more threaded interior walls 112 forreceiving and threadingly engaging with screw-type locking mechanisms85. The extended shape of the metallic insert 110 prevents any rotationof the insert 100 when the locking mechanism 85 is being inserted intoor removed from the plating system 30. Although the metallic insert 110is illustrated as a single unit, it may be comprised of multiple units.

In one embodiment, the metallic insert 110 is formed as a dove tail,with an upper surface (as shown in FIG. 7 c) that is larger than itslower surface. The dove tail shape of the metallic insert fits like a“key” into a corresponding slot 114 of the plate 31 i. In the presentembodiment, the dove tail shape also allows the insert 110 to be slidinto the plate 31 i, so that one or more of the threaded portions of theinsert are aligned with one or more of the bores 70. In someembodiments, a pin 116 may also (or alternatively) be used to secure themetallic insert 110 into the plate. It is known that there are manydifferent ways to secure the metallic insert 110 to the plate 31 i, andthe locking screws 85 themselves can be the sole source of securement.

The plating system 30 of FIGS. 7 a–7 c include many benefits. Inaddition to the benefits listed above with reference to FIGS. 1–6 c, themetallic inserts 110 provide extra strength for several differentlocking screws 85. A single metallic insert 110 can easily be slid intothe plate 31 i, thereby making manufacturing easier. Alternatively,several metallic plates (e.g., one for each locking screw 85) can besequentially slid into the slot 114 of the plate 31 i, thereby having areduced number of insert sizes accommodating the different potentialshapes and lengths (e.g., FIGS. 3 a–3 g) that may be used for the plate31 i.

Although only a few exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. For example, one or more visualizationwindows (apertures) can be made in the plate 31 to facilitate the visualplacement of the plating system by a surgeon. Also, features illustratedand discussed above with respect to some embodiments can be combinedwith features illustrated and discussed above with respect to otherembodiments. Accordingly, all such modifications are intended to beincluded within the scope of this invention.

We claim:
 1. A spinal plating system for promoting fusion between two ormore vertebral bodies, comprising: a plurality of bone screws; a bodyformed primarily of a non-metallic radiolucent material, the body havingan upper surface and a lower surface, wherein the body includes aplurality of bone screw openings for receiving the plurality of bonescrews, wherein the body includes at least one locking mechanism openingfor receiving a locking mechanism; and at least one insert formedprimarily of a metallic material, the insert being insertable into theat least one locking mechanism opening, wherein the insert selectivelyreceives the locking mechanism; wherein each of the at least one lockingmechanism openings is situated such that at least one of the pluralityof bone screws received in one of the plurality of bone screw openingsis lockably held by the received locking mechanism; wherein the at leastone insert includes a dove tail portion that longitudinally extendsalong a corresponding slot of the bottom surface of the body, andwherein the insert includes a plurality of threaded openings and thebody includes a plurality of locking mechanism openings positioned sothat when the dove tail portion of the insert is positioned in thecorresponding slot of the body, the plurality of threaded openings arealigned with the plurality of locking mechanism openings.
 2. A boneplate comprising: a body formed primarily of a first material, whereinthe body includes a plurality of openings for receiving a plurality ofattachment mechanisms; at least one insert including a second materialdifferent from the first material and a plurality of threaded engagingportions alignable with the plurality of openings of the body, theinsert further being shaped corresponding to a slot in the body tothereby secure the insert to the body and extend along a longitudinalaxis of the body for selectively engaging with a plurality of lockingmechanisms; and the plurality of locking mechanisms for engaging withthe plurality of engaging portions, so that at least one of the lockingmechanisms secures at least one attachment mechanism in a correspondingopening.
 3. The bone plate of claim 2 wherein the first material is apolymer.
 4. The bone plate of claim 3 wherein the first material ispolyetheretherketone (PEEK).
 5. The bone plate of claim 3 wherein thesecond material is a metal.
 6. The bone plate of claim 5 wherein thesecond material is selected from the group of metals consisting oftitanium and titanium alloys.
 7. The bone plate of claim 2 wherein theinsert and the slot in the body are dovetail shaped.
 8. The bone plateof claim 2 wherein at least one of the plurality of attachmentmechanisms is a bone screw.
 9. The bone plate of claim 8 wherein thebone screw is a fixed-angle screw.
 10. The bone plate of claim 8 whereinthe bone screw is a variable-angle screw.
 11. The bone plate of claim 2wherein the plurality of locking mechanisms are moveable between aloosely fixed position of engaging the plurality of engaging portionsthat allows the plurality of attachment mechanisms to be inserted intothe plurality of openings of the body and a locked position of engagingthe plurality of engaging portions that secures the plurality ofattachment mechanisms into the plurality of openings.